I/313 LQRF: Large Quasar Reference Frame (Andrei+, 2009)
The LQRF - An optical representation of the ICRS.
Andrei A.H., Souchay J., Zacharias N., Smart R.L., Vieira Martins R.,
da Silva Neto D.N., Camargo J.I.B., Assafin M., Barache C., Bouquillon S.,
Penna J.L., Taris, F.
<Astron. Astrophys. 505, 385 (2009)>
=2009A&A...505..385A 2009A&A...505..385A
ADC_Keywords: QSOs ; Positional data
Keywords: catalogs - reference systems - quasars: general -
methods: data analysis - astrometry
Abstract:
The LQRF (Large Quasar Reference Frame) was built with the care of
avoiding wrong matches of its constituents quasars, of homogenizing
the astrometry from the different catalogs and lists from which the
constituent quasars are gathered, and of attaining the milli-arcsec
global alignment to the ICRF (International Celestial Reference
Frame), as well as typical individual source position accuracies even
to better than 100 milli-arcsec. Starting from the updated and
presumably complete LQAC (Large Quasar Astrometric Catalog) list of
QSOs, initial optical positions for those quasars are found in the
USNO B1.0 and GSC2.3 catalogs, and from the SDSS Data Release 5. The
initial positions are next placed onto UCAC2 based reference frames,
following by an alignment to the ICRF, as well as of the most precise
sources from the VLBA calibrator list and from the VLA calibrator list
- when reliable optical counterparts exist. Finally the LQRF axes are
inspected through spherical harmonics, contemplating right ascension,
declination and magnitude terms.
Description:
The LQRF contains J2000 referred equatorial coordinates, and is
completed by redshift and photometry information from the LQAC.The
LQRF contains 100,165 quasars, well represented on all-sky basis, from
-83.5 to +88.5 degrees of declination, and with 10-arcmin as the
average distance between adjacent elements. The global alignment to
the ICRF is of 1.5mas, and the individual position accuracies are
represented by a Poisson distribution peaking at 139mas on right
ascension and at 130mas on declination.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
lqrf.dat 100 100165 J2000 equatorial coordinates catalog
--------------------------------------------------------------------------------
See also:
J/A+A/494/799 : Large Quasar Astrometric Catalogue (LQAC) (Souchay+, 2009)
I/251 : VLBI International Celestial Reference Frame (ICRF) (Ma+, 1997)
Byte-by-byte Description of file: lqrf.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right ascension (J2000.0)
4- 5 I2 min RAm Right ascension (J2000.0)
7- 13 F7.4 s RAs Right ascension (J2000.0)
15 A1 --- DE- Declination sign (J2000.0)
16- 17 I2 deg DEd Declination (J2000.0)
19- 20 I2 arcmin DEm Declination (J2000.0)
22- 27 F6.3 arcsec DEs [0,60] Declination (J2000.0)
29- 34 F6.1 mas e_RAs External RA error (RAcosDE)
36- 41 F6.1 mas e_DEs External DE error
43- 44 I2 --- Nr Number of radio interferometry neighbor
positions used to evaluate the external errors
46- 50 F5.2 --- Rmag Magnitude R (1)
52- 56 F5.3 --- z ? Redshift (1) (2)
58- 64 F7.1 mas oRA ? Right ascension offset to the radio position
counterpart (RAcosDEC) (2)
66- 72 F7.1 mas oDE ? Declination offset to the radio position
counterpart (2)
74- 75 I2 h RAr.h ? Right ascension of the radio position
counterpart (J2000.0) (2)
77- 78 I2 min RAr.m ? Right ascension of the radio position
counterpart (J2000.0) (2)
80- 86 F7.4 s RAr.s ? Right ascension of the radio position
counterpart (J2000.0) (2)
88 A1 --- DEr.- ? Declination sign of the radio position
counterpart (J2000.0) (2)
89- 90 I2 deg DEr.d ? Declination of the radio position
counterpart (J2000.0) (2)
92- 93 I2 arcmin DEr.m ? Declination of the radio position
counterpart (J2000.0) (2)
95-100 F6.3 arcsec DEr.s ? Declination of the radio position
counterpart (J2000.0) (2)
--------------------------------------------------------------------------------
Note (1): Data from the LQAC (Souchay et al., 2009, Cat. J/A+A/494/799).
Note (2): Blank when the data is not available.
--------------------------------------------------------------------------------
Acknowledgements:
Alexandre Humberto Andrei, oat1(at)on.br
(End) Alexandre H. Andrei [ON/MCT, Brasil], Patricia Vannier [CDS] 28-May-2009